System for operating an unattended automobile engine

ABSTRACT

A system for operating an unattended automobile engine. The normally open contacts of an electrical relay are connected in shunt across the movable contact and stationary ignition circuit contact of the ignition switch. The relay operating coil is energizable upon the operation of the ignition switch to the &#39;&#39;&#39;&#39;Crank&#39;&#39;&#39;&#39; and/or &#39;&#39;&#39;&#39;Run&#39;&#39;&#39;&#39; position and is maintained energized upon the operation of the ignition switch to the &#39;&#39;&#39;&#39;Off&#39;&#39;&#39;&#39; position through the relay contacts connected in shunt across the contacts of the ignition switch. The relay operating coil may be shunted by a normally open selector switch when it is desired to turn off the ignition system of the engine and is shunted by the normally open coolant temperature tell-tale lamp switch and the normally closed oil pressure tell-tale lamp switch to automatically turn off the ignition system of the engine in the event of overheating or loss of oil pressure.

United States Patent [191 1 1] 3,766,398 Ballou Oct. 16, 1973 SYSTEM FOROPERATING AN. Primary Examiner-G. R. Simmons UNATTENDED AUTOMOBILEENGINE [75] Inventor: Richard P. Ballou, Howell, Mich.

[733] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: June 15, 1972 [21] Appl. No.: 262,962

[52] US. Cl. 290/38, 290/37 [51] Int. Cl. H02p 9/04 [58] Field of Search290/33, 37, 38;

[56] References Cited umTio sflfes 'i A'reiq'is 3,587,545 6/1971 Ballou290/38 3,675,032 7/1972 Shaheen 290/38 C Attorney-Eugene W. Christen etal.

[57] ABSTRACT A system for operating an unattended automobile engine.The normally open contacts of an electrical relay are connected in shuntacross the movable contact and stationary ignition circuit contact ofthe ignition switch. The relay operating'coil is energizable upon theoperation of the ignition switch to the Crank and/or Run position and ismaintained energized upon the operation of the ignition switch to theOff position through the relay contacts connected in shunt across thecontacts of the ignition switch. The relay operating coil may be shuntedby a normally open selector switch when it is desired to turn off theignition system of the engine and is shunted by the normally opencoolant temperature tell-tale lamp switch and the normally closed oilpressure tell-tale lamp switch to automatically turn off the ignitionsystem of the engine in the event of overheating or loss of oilpressure.

5 Claims, 3 Drawing Figures TO ACCESSORY E c1Rcu|Ts To HEATER {AIR 7CONDITlONER M /63 67 g a 66 l r -OOLANT I m EMPERATUREF 1 i PESoURESWlTCH /L J L [SNITCH SYSTEM FOR OPERATING AN UNATTENDED AUTOMOBILEENGINE This invention is directed to a system for operating anunattended automobile engine and, more specifically, to a system of thistype which permits the operation of the automobile engine with theignition switch in the Off position and provides manual turnoff of theengine ignition circuit and automatic turnoff of the engine ignitioncircuit in the event the transmission is shifted to any position exceptPark or the engine overheats or loses oil pressure.

On many occasions it is desirable to operate the engine of an unattendedautomobile while the vehicle is locked without danger of theft or enginedamage. The primary applications would be for heating the automobileduring cold weather, for air conditioning the automobile during warmweather, or for permitting the engine to operate to charge thebattery'while unattended.

It is, therefore, an object of this invention to provide an improvedsystem for operating an unattended automobile engine.

It is another object of this invention to provide an improved systemforoperating an unattended automobile engine while the ignition switchis in the Off or Lock position.

It is an additional object of this invention to provide an improvedsystem for operating an unattended automobile engine while the ignitionswitch is in thefLock .or.0ff position and which provides for the manualturnoff of the engine ignition circuit when desired and for theautomatic turnoff of the engine ignition circuit in the event thetransmission is shifted to any position except the Park position or theengine overheats or loses oil pressure.

In accordance with this invention, a system for operating an unattendedautomobile engine is provided wherein the normally open contacts of anelectrical relay are connected in shunt across the movable contact andstationary ignition circuit contact of the ignition switch with therelay operating coil, connected in series with the transmission neutralswitch across the battery, energizable upon the operation of theignition switch to the Crank and/or Run position, maintained energizedupon the operation of the ignition switch to the Off" position throughthe stationary and movable contacts of the relay shunted manually by anormally open selector switch to manually turn off the ignition circuitof the engine and shunted by the normally open coolant temperaturetell-tale lamp switch and the normally closed oil pressure tell-talelamp switch to automatically turn off the ignition circuit of the enginein the event of overheating or loss of oil pressure.

For a better understanding of the present invention, together withadditional objects, advantages and features thereof, reference is madeto the following description and accompanying drawing in which:

.FIG. 1 schematically setsforth the system of this invention foroperating an unattended automobile engine with a selector switch featurewhich provides for the selective energization and d eenergization of thesystem;

FIG. 2 schematically sets forth the system of this in vention which isautomaticallyenergized upon the operation of the ignition switch to the"Run position and is deenergized automatically upon the shifting of thetransmission to any position except the Neutral or Park position; and

FIG. 3 sets forth schematically the system of this invention whichprovides an auxiliary set of relay contacts through which the heater andair conditioning equipment may be energized.

In the FIGURES of the drawing, like elements have been assigned likecharacters of reference.

As the point of reference or ground potential is the same pointelectrically throughout the system, it has been represented in FIG. 1 bythe accepted schematic symbol and referenced by the numeral 5.

Referring to FIG. 1 of the drawing, the system for operating anunattended automobile engine of this invention is set forth incombination with an ignition switch 10 having a movable contact 11 and astationary ignition circuit contact 13, a transmission neutral switch15, a normally open coolant temperature tell-tale light switch 17, anormally closed oil pressure tell-tale light switch 19 and a directcurrentpotential source having positive and negative polarity terminals,which may be a battery 8.

Ignition switch 10 may be any conventional automotive type ignitionswitch having an open or Off position, in which position it isillustrated in FIG. 1, a Run position, at which movable contact 11 isclosed to accessory circuit stationary contact 12 and ignition circuitstationary contact 13, and a Crank position, at which movable contact 11is closed to ignition circuit stationary contact 13 and cranking circuitstationary contact 14. As is well known in the automotive art,

ignition switches of this type are spring biased to automatically returnto the Run position wherein movable contact 11 is closed to accessorycircuit stationary contact 12 and ignition circuit stationary contact 13when the torque applied to the ignition key is released upon'enginestart. The transmission neutral switch 15 may be a conventionalautomotive type transmission neutral switch having a movable contactwhich is operated to the electrical circuit closed condition with astationary contact while the transmission is shifted into the Park orNeutral position and to the electrical circuit open condition in anyother transmission position, coolant temperature tell-tale light switch17 may be a conventional automotive type coolant temperature switchhaving two normally open temperature sensitive contacts which operate tothe electrical circuit closed condition when the coolant temperaturereaches a predetermined magnitude and oil pressure tell-tale lightswitch19may be a conventional automotive type oil pressure switch havingtwo normally closed pressure sensitive contacts which are operated tothe electrical circuit open condition by normal engine lubricating oilpressure. All of these three switches are commercially available itemswell known in the art which are installed upon all modern automobiles.

- Upon the operation of movable contact 1 l of ignition I movablecontact 11 and ignition circuit stationary contact 13 of ignition switch10, lead 23, ignitioncoil primary winding 24, ignition distributorbreaker contacts 25 and 26 and point of reference or ground potential 5and battery 8 potential is applied to the coolant temperature tell-talelamp 16 and the oil pressure tell-tale lamp 18 through lead 28 and tothe heater and air conditioner circuit through lead 29. The ignitiondistributor breaker contacts 25 and 26 are operated to the electricalcircuit open and closed conditions in timed relationship with theengine, not shown, in a manner well known in theautomotive art toprovide ignition signal pulses in the ignition coil secondary winding27. Upon engine start andthe operation of movable contact ll of ignitionswitch to the Run position, the energizing circuit for cranking motorsolenoid 20 is interrupted, battery 8 potential is maintained upon thetell-tale lamps and heater and air conditioner circuit and battery-8potential is applied to the accessory circuit through lead 30. Thisportion of FIG. 1 is old and well known in the automotive art and, perse, forms no part of this invention. I

The system of this invention for operating an unattended automobileengine is comprised of a two-pole, single-throw relay 35 havinganoperating coil36, two stationary contacts 37 and 39, and two movablecontacts 38 and 40, each corresponding to one of the stationarycontacts, operable to the electrical circuit closed position upon theenergization of operating coil 36 and a manually operable single pole,double-throw selector switch 45 having two stationary contacts 46 and47'and a movable contact 48 having a center electric circuit openposition, in which position it is illustrated in FIG. 1, and operable tothe electric circuit closed position with each of stationary contacts 46and Movable contact 38 and stationary contact 37 of relay 35 areconnected in shunt across the movable contact 11 and the stationaryignition circuit contact- 13 of ignition switch 10 through junction 41and lead 50 and through lead 51, junction 42 and lead 23.

One end of the relay operating coil 36 is connected to aselectedpolarity terminal of the direct current potential source through thetransmission neutral switch. In FIG. 1, and without intention orinference of a limitation thereto, end 36b of relay operating coil. 36is connected to thenegative polarity terminal of battery 8 throughlead'52 forward poled diode 53, junction 43, lead 22, transmissionneutral switch 15, cranking motor solenoid;20 and point of reference orground potential The other end of relay-operating coil 36 is connectedto the other polarity terminal of the direct current potential.sourcethrough firstand second circuits. In FIG. 1, and withoutintention orinference ofva limitation thereto, end 36a of relay"operating 36 is connected to the positive polarity terminal of battery 8through a first circuit which may be tracedfrom the positive polarityterminal of battery 8, through lead 2l, movab le contact 11 and ignitioncircuit stationary contact 13 of ignition switch 10, leads 23 and 51,current limiting resistor 55, lead 56, stationary contact 46 and movablecontact 48' of selector switch 45 and leads 57, 58 and 59 and through asecond circuit which may be traced from the positive polarity terminalof battery 8 through leads 21 and 50, movable contact 38 and stationarycontact 37 of relay 35, resistor 55, lead 60, stationary contact 39and'corresponding movable contact 40 of relay 35 and leads 58 and 59.

The movable contact and the other one of the stationary contacts ofselector switch 45 are connected in shunt across relay operating coil 36through a circuit which may be traced from end 36a of relay operatingcoil 36, through leads 59, 58 and 57, movable contact 48 and stationarycontact 47 of selector switch 45 and point of reference or groundpotential 5.

The series combination of a forward poled diode 65 and the normally opencoolant temperature tell-tale light switch 17 is connected in shuntacross relay operating coil 36 through a circuit which may be tracedfrom end 36a of relay operating coil 36 through leads 59 and 58,junction 44, lead 61, forward poled diode 65, leads 62 and 63, coolanttemperature switch 17 and point of reference or ground potential 5.

The series combination of forward poled diode 66 and the normally closedoil pressure tell-tale light switch 19 is connected in shuntacross relayoperating coil 36 through a circuit which may be traced from end 36a ofrelay operating coil 36, through leads S9 and 58, junction 44, lead 64,forward poled diode 66, leads 67 and 68, oil pressure tell-tale lightswitch 19 and point of reference or ground potential 5.

With the engine running and the transmission shifted to the Park orNeutral position, movable contact 11 of ignition switch 10 is closed tothe ignition circuit stationary contact 13. Upon the operation ofmovable contact 48 of selector switch 45 into electrical contact withstationary contact 46, relay operating coil 36 is energized by battery 8through a circuit which may be. traced from the positive-polarityterminal'of battery 8, through lead 21, movable contact 11 and ignitioncircuit stationary contact 13 of ignition switch 10, leads 23 and 51,resistor 55, lead 56,-stationary contact 46 and movable contact 48 ofselector switch 45, leads 57, 58 and '59, relay operating coil 36, lead52, forward poled diode 53, junction 43, lead 22, transmission neutralswitch 15, low resistance cranking motor solenoid 20 and point ofreference or ground potential 5 to the negative polarity terminal ofbattery 8. The energization of relay operating coil 36 operates movablecontacts 38 and 40 into electrical contact with corresponding stationarycontacts 37 and 39, respectively. Mov-' able contact 38 and stationarycontact 37 provide a shunt circuit across movable contact 11 andignition circuit stationary contact 13 of ignition switch10 and,

with stationary contact 39 and movable contact 40 of operating coil 36,lead 52, forward poled diode 53,1

junction 43, lead 22, transmission neutral switch 15, low resistancecranking motor solenoid 20 and point of reference or ground potential 5to the negative polarity terminal of battery 8. Consequently, upori the'energi'za-- tion ofrelay 35, the ignition switch 10 may be operated tothe Off position and the ignition" key withdrawn and the engine ignitioncircuit, the tell-talelamp 'circuits and the heater and air conditionercircuit are maintained through'leads 21 and 50, movable contact 38 andstationary contact 37 of relay 35 and leads 51,

'. 23, 28 and 29. The engine, therefore, will continue to run and theheater and/or air conditioner will operate,

provided the individual switch which energizes each of these respectivedevices is in the electrical circuit closed condition.

In the event the transmission lever should be shifted out of the Park orNeutral position, the transmission neutral switch will interrupt theenergizing circuit for relay operating coil 36 to deenergize this relay.Upon the deenergization of relay 35, the ignition circuit and thetell-tale lamp and heater and air conditioner circuits are interruptedby movable contact 38 moving out of electrical contact with stationarycontact 37 of relax 35, a condition which turns off the engine ignitioncircuit to stop the engine.

In the event the coolant temperature should reach a predeterminedmaximum magnitude, the normally open contacts of coolant temperatureswitch 17 will be operated to the electrical circuit closed condition toprovide a low resistance shunt circuit across relay operating coil 36and should the engine lose oil pressure, the normally closed contacts ofoil pressure switch 19 will operate to the electrical circuit closedcondition to also provide a low resistance shunt circuit across relayoperating coil 36. Upon the closure of either the coolant temperatureswitch 17 or the coil pressure switch 19, operating coil 36 of relay 35becomes deenergized and, consequently, movable contact 38 moves out ofelectrical contact with stationary contact 37 to interrupt the ignition,tell-tale lamp and heater and air condition circuits.

Diode 53 is inserted in series with relay operating coil 36 andtransmission neutral switch 15 to prevent the energization of relayoperating coil 36 by a reverse power flow therethrough during enginecranking through diode 66 and the oil pressure switch 19 to point ofreference or ground potential 5.

Diodes 65 and 66 isolate the coolant temperature switch tell-tale lampand oil pressure switch tell-tale lamp circuits from each other.

If desired, diode 65 may be omitted, a condition which will permit thechecking of the coolant temperature tell-tale lamp 16 upon starting, asground therefor will be supplied through diode 66 and the oil pressureswitch 19. I

The circuit may be made completely automatic by eliminating selectorswitch 45 and movable-contact 40 and stationary contact 39'of relay 35so that resistor 55 is connected directly to end 36a of relay'operatingcoil 36 through leads 56,57, 58 and 59 as shown in FIG. 2, whichschematically sets forth only this portion of the circuit. With thismodification, relay operating coil 36 will be energized whenever theengine is running and the transmission is shifted to the Park or Neutralpositions. To allow the engine to remain running, the transmission isshifted to the Park position before the ignition switch 10 isv operatedto its Off position. To stop the engine, the ignition switch 10 isoperated to the Offiposition before the transmission is shifted into thePark. position. v

On some recent model year automobiles, the heater and air conditionercircuit is not supplied through the movable contact and ignition circuitstationary contact of the ignition switch but is supplied by anadditional circuit within the ignition switch so that these accessoriesare disconnected during engine cranking. With automobiles of this type,an additional movable contact 70 and an additional correspondingstationary contact 71 may be added to relay 35 to complete an energizingcircuit for the heater and air conditioner while the ignition switch isin the Run position, as schematically shown in FIG. 3.

While this specification has indicated the negative polarity terminalbattery 8 to be connected to point of reference or ground potential 5,it is to be specifically understood that the circuit of this inventionis equally applicable with systems in which the positive polarityterminal of the battery is connected to point of reference or groundpotential 5.

While a preferred embodiment of the present invention has been shown anddescribed, it will be obvious to those skilled in the art that variousmodifications and substitutions may be made without departing from thespirit of the invention which is to be limited only within the scope ofthe appended claims.

What is claimed is:

1. A system for operating an unattended automobile engine comprising incombination with an ignition switch having a movable contact and astationary ignition circuit contact, a transmission neutral switch, anormally open coolant temperature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch and a direct currentpotential source having pos- .itive and negative polarity terminals; arelay having an operating coil and at least one stationary contact and acorresponding movable contact, operable to the electrical circuit closedposition upon the energization of said operating coil, connected ins'hunt across said movable contact and said stationary ignition circuitcontact of said ignition switch; a resistor; means for connecting oneend of said relay operating coil to a selected polarity terminal of saiddirect current potential source through said transmission neutralswitch; first circuit means for connecting the other end of said relayoperating coil to the other polarity terminal of said direct currentpotential source through said movable contact and said stationaryignition circuit contact of said ignition switch and said resistor;second circuit means for connecting the said other end of said relayoperating coil to the said other polarity terminal of said directcurrent potential source through said stationary'contact and the saidmovable contact of said relay and said resistor; means for connectingsaid normally open coolant temperature tell-tale light switch in shuntacross said relay operating coil; and means for connecting said normallyclosed oil pressure tell-tale light switch in shunt across said relayoperating coil.

2. A system for operating an unattended automobile engine comprising incombination with an ignition switch having a movable contact and astationary ignition circuit contact, a transmission neutral switch, anormally open coolant temperature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch anda direct current potentialsource having positive and negative polarity terminals; a relay havingan operating coil and at least one stationary contact and acorresponding movable contact, operable to the electrical circuit closedposition upon the energization of said operating coil, connected inshunt across said movable contact and said stationary ignition circuitcontact of said ignition switch; a resistor; a first diode; means forconnecting one end of said relay operating coil to a selected polarityterminal of said direct current potential source through said firstdiode and said transmission neutral switch in series; first circuitmeans for connecting the other end of said relay operating coil to theother polarity terminal of said direct current potential source throughsaid movable contact and said stationary ignition circuit contact ofsaid ignition switch said normally closed oil pressure tell-tale lightswitch in shunt across said relay operating coil.

3. A system for operating an unattended automobile engine comprising incombination with an ignition switch having a movable contact and astationary ignition circuit contact, a transmission neutral switch, anormally open coolant temperature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch and a direct currentpotential source having positive and negative polarity terminals; atwo-pole single.- throw relayhaving an operating coil, two stationarycontacts and two movable contacts, each corresponding to one ofsaid'stationary contacts, operable to the electrical circuit closedposition upon the energization of said operating coil; means forconnecting one of said stationary contacts and one'of said movablecontacts of said relay in shunt across said movable contact and saidstationary ignition circuit contact of said ignition switch; asingle-pole double-throw selector switch having two'stationary-contactsand a movable contact having a center electric circuit open position andoperable to the electrical closed position with each of said stationarycontacts; a resistor; means for connecting one end of said relayoperating coil tov a selected polarity terminal of said direct currentpotential source through said transmission neutral switch; first'circuitmeans for connecting the other end of said relay operating coil to thesaid oneof said stationary contacts andthe corresponding said movablecontact of said relay connected in shunt across said movable .contactandsaid stationary ignition contact of said ignition switch, said resistorI and the other one :of saidstationary contacts and the correspondingsaid movable contact ofsaid relay in series; means forconnecting saidmovable contact and the other one of said-stationary contacts of saidselector switch in shuntacross said relay operating coil; means forconnecting saidnormally open coolant temperature tell-tale light switchin shunt] across said relay operating coil; and means for connectingsaid normally closed oil pressure tell-tale light switch in shunt acrosssaid relay operating coil. v e

4. A system for operating an unattend'ed automobile engine comprising incombination with an ignition switch having a movable contact and a'stationary ignition circuit contact, a transmission neutral switch, anormally open coolant temperature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch and a direct currentpotential source having positive and negative polarity terminals; atwo-pole singlethrow relay having an operating coil, two stationary.contacts and two movable contacts, each corresponding to one of saidstationary contacts, operable to the electrical circuit closed positionupon the energization of said operating coil; means for connecting oneof said stationary contacts and one of said movable contacts of saidrelay in shunt across said movable contact and said stationary ignitioncircuit contact of said ignition switch; a single-,pole-double-throwselector switch hav-* ing two stationary contacts and a movable contacthaving a center electric circuit open position and operable to theelectrical closed position with each of said stationary contacts; aresistor; a first diode; means for connecting one end of said relayoperating coil to a selected polarity terminal if said direct currentpotential source through said first diode and said transmission neutralswitch in series; first circuit means for connecting the other end ofsaid relay operating coil to theother polarity terminal of saiddirectcurrent potential source through said movable contact and saidstationary ignition circuit contact of said ignition switch, saidresistor and one of said stationary contacts and said movable contact ofsaid selector switch in series; second circuit means for connecting thesaid other end of said relay operating coil to the said other polarityterminal of said direct current potential source'through said one ofsaid stationary contacts and the corresponding said movable contact ofsaid relay, said resistor and a two-pole single-throw relay having anoperating'coil,- 1

. and a movable contact having a center electric circuit normally closedoil pressureitell-tale light switch in shunt across said relay operatingcoil. 1 1

5. A system for operating an unattended automobile engine comprising incombination with an ignition switch having a movable contact and astationary ignition circuit contact, a transmission neutral switch, a

normally open coolanttemperature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch and a direct currentpotential source-having positive and negative polarity terminals, one ofwhich is connected to a point of reference or ground potential;

two stationary contacts and two movable contacts, eachicorresponding toone of said stationary contacts,

operable to the'electrical circuit closed position upon the energizationof saidoperatin'g'coil; means for con-' necting one of said stationarycontacts and'oneof said movable contacts of said relay in shunt acrosssaid movable contact and said stationary ignition circuit contact ofsaid ignition switch; a single-pole double throw selector switch havingtwo stationary contacts open position and operable to the electricalclosed position with each of said stationary contacts; a resistor; afirst diode; means for connecting one end of said relay operating coilto said point of reference or ground potential through said first diodeand said transmission neutral switch in series; first circuit means forconnecting the other end of said relay operating coil to the ungroundedpolarity terminal of said direct current potential source through saidmovable contact and said stationary ignition circuit contact of saidignition switch, said resistor and one of said stationary contacts andsaid movable contact of said selector switch in series; second circuitmeans for connecting the said other end of said relay operating coil tothe ungrounded polarity terminal of said direct current potential sourcethrough said one of said stationary contacts and the corresponding saidmovable contact of said relay, said resistor and the other one of saidstationary contacts and the corresponding said movable contact of saidrelay in series; means for connecting said movable contact and the otherone of said stationary contacts of said selector switch in shunt acrosssaid relay operating coil; second and third diodes; means for connectingthe series combination of said second diode and said normally opencoolant temperature tell-tale light switch in shunt across said relayoperating coil; and means for connecting the series combination of saidthird diode and said normally closed oil pressure tell-tale light switchin shunt across said relay operating coil.

1. A system for operating an unattended automobile engine comprising incombination with an ignition switch having a movable contact and astationary ignition circuit contact, a transmission neutral switch, anormally open coolant tempErature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch and a direct currentpotential source having positive and negative polarity terminals; arelay having an operating coil and at least one stationary contact and acorresponding movable contact, operable to the electrical circuit closedposition upon the energization of said operating coil, connected inshunt across said movable contact and said stationary ignition circuitcontact of said ignition switch; a resistor; means for connecting oneend of said relay operating coil to a selected polarity terminal of saiddirect current potential source through said transmission neutralswitch; first circuit means for connecting the other end of said relayoperating coil to the other polarity terminal of said direct currentpotential source through said movable contact and said stationaryignition circuit contact of said ignition switch and said resistor;second circuit means for connecting the said other end of said relayoperating coil to the said other polarity terminal of said directcurrent potential source through said stationary contact and the saidmovable contact of said relay and said resistor; means for connectingsaid normally open coolant temperature tell-tale light switch in shuntacross said relay operating coil; and means for connecting said normallyclosed oil pressure tell-tale light switch in shunt across said relayoperating coil.
 2. A system for operating an unattended automobileengine comprising in combination with an ignition switch having amovable contact and a stationary ignition circuit contact, atransmission neutral switch, a normally open coolant temperaturetell-tale light switch, a normally closed oil pressure tell-tale lightswitch and a direct current potential source having positive andnegative polarity terminals; a relay having an operating coil and atleast one stationary contact and a corresponding movable contact,operable to the electrical circuit closed position upon the energizationof said operating coil, connected in shunt across said movable contactand said stationary ignition circuit contact of said ignition switch; aresistor; a first diode; means for connecting one end of said relayoperating coil to a selected polarity terminal of said direct currentpotential source through said first diode and said transmission neutralswitch in series; first circuit means for connecting the other end ofsaid relay operating coil to the other polarity terminal of said directcurrent potential source through said movable contact and saidstationary ignition circuit contact of said ignition switch and saidresistor; second circuit means for connecting the said other end of saidrelay operating coil to the said other polarity terminal of said directcurrent potential source through said stationary contact and the saidmovable contact of said relay and said resistor; second and thirddiodes; means for connecting the series combination of said second diodeand said normally open coolant temperature tell-tale light switch inshunt across said operating coil; and means for connecting the seriescombination of said third diode and said normally closed oil pressuretell-tale light switch in shunt across said relay operating coil.
 3. Asystem for operating an unattended automobile engine comprising incombination with an ignition switch having a movable contact and astationary ignition circuit contact, a transmission neutral switch, anormally open coolant temperature tell-tale light switch, a normallyclosed oil pressure tell-tale light switch and a direct currentpotential source having positive and negative polarity terminals; atwo-pole single-throw relay having an operating coil, two stationarycontacts and two movable contacts, each corresponding to one of saidstationary contacts, operable to the electrical circuit closed positionupon the energization of said operating coil; means for connecting oneof said stationary contacts and one of said movable contacts of saIdrelay in shunt across said movable contact and said stationary ignitioncircuit contact of said ignition switch; a single-pole double-throwselector switch having two stationary contacts and a movable contacthaving a center electric circuit open position and operable to theelectrical closed position with each of said stationary contacts; aresistor; means for connecting one end of said relay operating coil to aselected polarity terminal of said direct current potential sourcethrough said transmission neutral switch; first circuit means forconnecting the other end of said relay operating coil to the otherpolarity terminal of said direct current potential source through saidmovable contact and said stationary ignition circuit contact of saidignition switch, said resistor and one of said stationary contacts andsaid movable contact of said selector switch in series; second circuitmeans for connecting the said other end of said relay operating coil tothe said other polarity terminal of said direct current potential sourcethrough the said one of said stationary contacts and the correspondingsaid movable contact of said relay connected in shunt across saidmovable contact and said stationary ignition contact of said ignitionswitch, said resistor and the other one of said stationary contacts andthe corresponding said movable contact of said relay in series; meansfor connecting said movable contact and the other one of said stationarycontacts of said selector switch in shunt across said relay operatingcoil; means for connecting said normally open coolant temperaturetell-tale light switch in shunt across said relay operating coil; andmeans for connecting said normally closed oil pressure tell-tale lightswitch in shunt across said relay operating coil.
 4. A system foroperating an unattended automobile engine comprising in combination withan ignition switch having a movable contact and a stationary ignitioncircuit contact, a transmission neutral switch, a normally open coolanttemperature tell-tale light switch, a normally closed oil pressuretell-tale light switch and a direct current potential source havingpositive and negative polarity terminals; a two-pole single-throw relayhaving an operating coil, two stationary contacts and two movablecontacts, each corresponding to one of said stationary contacts,operable to the electrical circuit closed position upon the energizationof said operating coil; means for connecting one of said stationarycontacts and one of said movable contacts of said relay in shunt acrosssaid movable contact and said stationary ignition circuit contact ofsaid ignition switch; a single-pole double-throw selector switch havingtwo stationary contacts and a movable contact having a center electriccircuit open position and operable to the electrical closed positionwith each of said stationary contacts; a resistor; a first diode; meansfor connecting one end of said relay operating coil to a selectedpolarity terminal if said direct current potential source through saidfirst diode and said transmission neutral switch in series; firstcircuit means for connecting the other end of said relay operating coilto the other polarity terminal of said direct current potential sourcethrough said movable contact and said stationary ignition circuitcontact of said ignition switch, said resistor and one of saidstationary contacts and said movable contact of said selector switch inseries; second circuit means for connecting the said other end of saidrelay operating coil to the said other polarity terminal of said directcurrent potential source through said one of said stationary contactsand the corresponding said movable contact of said relay, said resistorand the other one of said stationary contacts and the corresponding saidmovable contact of said relay in series; means for connecting saidmovable contact and the other one of said stationary contacts of saidselector switch in shunt across said relay operating coil; second andthird diodEs; means for connecting the series combination of said seconddiode and said normally open coolant temperature tell-tale light switchin shunt across said relay operating coil; and means for connecting theseries combination of said third diode and said normally closed oilpressure tell-tale light switch in shunt across said relay operatingcoil.
 5. A system for operating an unattended automobile enginecomprising in combination with an ignition switch having a movablecontact and a stationary ignition circuit contact, a transmissionneutral switch, a normally open coolant temperature tell-tale lightswitch, a normally closed oil pressure tell-tale light switch and adirect current potential source having positive and negative polarityterminals, one of which is connected to a point of reference or groundpotential; a two-pole single-throw relay having an operating coil, twostationary contacts and two movable contacts, each corresponding to oneof said stationary contacts, operable to the electrical circuit closedposition upon the energization of said operating coil; means forconnecting one of said stationary contacts and one of said movablecontacts of said relay in shunt across said movable contact and saidstationary ignition circuit contact of said ignition switch; asingle-pole double-throw selector switch having two stationary contactsand a movable contact having a center electric circuit open position andoperable to the electrical closed position with each of said stationarycontacts; a resistor; a first diode; means for connecting one end ofsaid relay operating coil to said point of reference or ground potentialthrough said first diode and said transmission neutral switch in series;first circuit means for connecting the other end of said relay operatingcoil to the ungrounded polarity terminal of said direct currentpotential source through said movable contact and said stationaryignition circuit contact of said ignition switch, said resistor and oneof said stationary contacts and said movable contact of said selectorswitch in series; second circuit means for connecting the said other endof said relay operating coil to the ungrounded polarity terminal of saiddirect current potential source through said one of said stationarycontacts and the corresponding said movable contact of said relay, saidresistor and the other one of said stationary contacts and thecorresponding said movable contact of said relay in series; means forconnecting said movable contact and the other one of said stationarycontacts of said selector switch in shunt across said relay operatingcoil; second and third diodes; means for connecting the seriescombination of said second diode and said normally open coolanttemperature tell-tale light switch in shunt across said relay operatingcoil; and means for connecting the series combination of said thirddiode and said normally closed oil pressure tell-tale light switch inshunt across said relay operating coil.